Abstract: How to improve the thermal performance of exhaust airflow heat recovery system of mine fan diffuser is a frontier problem in green mine technology. In order to solve this problem, based on finite-time thermodynamics, the air heat pump used to improve the heat and humidity energy grade of exhaust air was used to obtain the cycle equations of ininvertible temperature and heat source, and the analytical expression of exergy profit rate about ambient temperature was derived and the expression of dimensionless exergy profit rate was defined. Used this expression and combined with the actual working conditions in period of the most difficult supply, the exergy profit rates of 6 cities are compared by every day and every hour. The results show that the suitable region of exhaust airflow heat recovery system is characterized by climate division. Especially, this system is suitable for temperate continental climate areas. In the subtropical monsoon climate areas, the change curve of exergic profit margin function in a single day is similar to the shape of “M”, and it is implacable that the revenue generated in the operation of exhaust airflow heat recovery system should be unstable. To avoid losses caused by continuous operation, it is necessary to formulate the start-stop strategy of heat recovery system, and a start-stop control method is proposed, and the benefits of the system throughout the application are calculated numerically. By comparison, the economic return is significantly improved after adopting this control method, and the maximum dimensionless exergy profit rate can be increased from -0.33 to 0.02, by an increment of 0.35.